In recent years, transmission speed and information capacity of wireless communications are increased in an exponential rate, driven by the increasing demand for short-range wireless communications, wireless local area networks (WLANs), and personal mobile communications devices. For these related applications, Federal Communications Commissions (FCC) specified in February 2002 that ultra-wideband communications technologies are to be used for commercial communications and for high-speed, low-power and short-range communications. In addition, Institute of Electrical and Electronic Engineering (IEEE) also proposed a new standard, IEEE 802.15 WPAN (wireless personal area network), for mobile communications consumer devices to provide high-speed and low-power ultra-wideband communications. However, over the designated UWB frequency band, there are existing WLAN operating bands such as the 5.2 GHz (5150–5350 MHz) and 5.8 GHz (5725–5825 MHz) bands, which may cause interference with the UWB operations. To prevent the interference from the WLAN system, the ultra-wideband communications system conventionally requires that the employed ultra-wideband antenna be connected to an external band-stop filter to block the WLAN signals. This approach, however, increases the production cost and the design complexity of the system circuitry.
Schantz et al. disclosed ultra-wideband monopole and dipole antennas in U.S. Pat. No. 6,774,859 issued in 2002. The technique incorporates one or more slits and one or more curved narrow slots on a metal plate of the antenna. An antenna as such exhibits multiple operation bands or a destructive band to cast out the frequency range overlapping with other communications systems. The major disadvantage of the prior art lies in that the antenna requires a very large metal plate and is too difficult to be integrated with the ground plate of the antenna's RF circuitry.
Accordingly, an ultra-wideband planar antenna is provided herein so as to achieve ultra-wideband operation, suppress interference, and be integrated with the antenna system's ground plate.